"Yaz and Yasmin are among Bayer’s top selling pharmaceutical products. According to the German drug manufacturer, over 4 million women worldwide use Yasmin alone. But the drug has also sparked growing controversy in recent months. A series of studies published in BMJ have shown that users of pills containing drospirenone have an increased risk of blood clots, which can cause deep vein thrombosis, pulmonary embolism, stroke, heart attack and death. And thousands of women have filed a lawsuit against Bayer, saying they were injured by Yaz or Yasmin.

Other Bayer products containing the hormone drospirenone are Beyaz and Safyral. In addition, four companies—Bayer, Teva, Watson and Sandoz—sell five generic versions of the drugs evaluated by the committee last month.

The FDA’s decision not to reveal its advisors’ relationships with the drugs’ manufacturers and Bayer raises serious questions about the agency’s treatment of potential conflicts of interest, a historically problematic area for the department. In 2004, controversy erupted over another FDA advisory hearing—involving the painkiller Vioxx—when it became clear that advisors with financial conflicts of interest were more likely than those without conflicts to vote that Vioxx was safe and should be allowed to stay on the market. The drug was ultimately withdrawn after a study showed it was associated with approximately 60,000 deaths. In 2008, partly in response to this uproar, the agency issued a new guidance on how to handle conflicts of interest among its advisors, stating that it wanted to reduce “bias” and to be more “transparent.”